JP2932663B2 - Driving device having piezoelectric element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device having a piezoelectric element mainly used for a dot print head.

[Prior Art] A piezoelectric element has electrodes adhered to both surfaces of a piezoelectric ceramic, and expands and contracts by increasing and decreasing an applied voltage. Driving an object to be driven by using the expansion and contraction has been already performed. I have. The piezoelectric element expands and contracts in response to an increase and decrease in the applied voltage. However, since the amount of expansion and contraction is small, the piezoelectric element is often used as a laminated piezoelectric element having a large amount of expansion and contraction. The laminated piezoelectric element expands in the laminating direction by increasing the applied voltage and contracts by decreasing the applied voltage. On the other hand, in the direction perpendicular to the stacking direction, the applied voltage contracts due to the increase in voltage, and expands due to the decrease.
In the conventional driving device, only expansion and contraction in the stacking direction is used for driving. That is, one end in the stacking direction is fixed to the frame, and an actuator is provided on the other end, so that expansion and contraction of the laminated piezoelectric element is transmitted to the driven object by the actuator.

FIG. 5 shows an example of this type of driving device. This driving device is a frame 80 (main frame 2, sub-frame 2) having a vertical effect laminated piezoelectric element 70 that expands and contracts the piezoelectric longitudinal effect by applying a voltage, and a base 3 that supports one end of the vertical effect laminated piezoelectric element 70 in the expansion and contraction direction. 4) and
A movable element 5 connected to the other end of the vertical effect laminated piezoelectric element 70 in the expansion and contraction direction, and an actuator connected to the movable element 5 and transmitting the expansion and contraction movement of the vertical effect laminated piezoelectric element 70 to a driven object. And

This operating device includes an Eden spring 67 comprising a pair of leaf springs 6, 7 having one end fixed to the main frame 2 and the mover 5, and a tilting body 8 connecting the other ends of the leaf springs 6, 7. The expansion / contraction movement of the longitudinal effect laminated piezoelectric element 70 due to the application of a voltage and the interruption of the application is converted into the tilting movement of the tilting body 8 by using the bending of the leaf springs 6 and 7. This tilting motion is transmitted to the arm 10, and the printing wire 11 is driven. The dot impact type printing apparatus is configured by arranging and attaching a necessary number (the same number of printing wires 11) of such driving devices to the holding member.

[Problems to be Solved by the Invention] However, this driving device has several problems. For example, when assembling a dot impact printing device having a large number of dots, each drive device corresponding to one dot is composed of one laminated piezoelectric element, one actuator, and one frame. Only the number of dots is required. For this reason, the number of parts is increased and productivity is extremely deteriorated. In addition, the entire printing device becomes large,
The weight increases.

Furthermore, the frame fixing one end of the laminated piezoelectric element absorbs the displacement of the element. To avoid this, it is necessary to increase the rigidity of the frame by, for example, increasing the cross-sectional area of each frame. is there. However, as a result, the entire driving device becomes large, and it is inevitable that the cost and weight increase, so that the rigidity cannot be increased so much.

Also, as shown in FIG. 6, since the longitudinal effect laminated piezoelectric element 70 has a stretching direction and a laminating direction that match, the longitudinal effect laminated piezoelectric element 70 has a tensile strength in the stretching direction and a tensile strength in the direction perpendicular to the stretching direction. The bending strength is lower than the piezoelectric ceramic layer 42 in terms of tensile strength, bending strength,
Alternatively, it depends on the bonding strength between the internal electrode layer 41 and the piezoelectric ceramic layer. (The arrow 45 indicates the polarization direction.) Therefore, the longitudinal effect laminated piezoelectric element 70 has a structure that is weak against the tensile force in the expansion and contraction direction and the bending force in the direction perpendicular to the expansion and contraction direction.

Here, in the above-described driving device, when the voltage application to the longitudinal effect laminated piezoelectric element 70 is cut off and the longitudinal effect laminated piezoelectric element 70 starts to contract, the mover 5 and the tilting body 8 are still moved by the inertia due to the inertia. There is a lot of movement in the direction of expansion and contraction of 70, and this return is delayed, and a tensile force is applied to the longitudinal effect laminated piezoelectric element 70. There is a problem that the tensile force causes damage to the longitudinal effect laminated piezoelectric element 70.

Further, even if the mover 5 is used, even if the four-bar parallel link 16 is used, the mover 5 does not accurately move in the vertical direction in the drawing, but moves while tilting (hereinafter referred to as tilting motion). For this reason, the tilting movement of the mover 5 is caused by the vertical effect laminated piezoelectric element.
When the bending effect is applied to the longitudinal effect laminated piezoelectric element 70 and transmitted to the longitudinal effect laminated piezoelectric element 70, the longitudinal effect laminated piezoelectric element 70 is broken.

In addition, unlike the other components, the longitudinal effect laminated piezoelectric element 70 has a negative linear expansion coefficient (for example, −6.0 [× 10 ⁻⁶ / ° C]), it is necessary to correct the amount of expansion due to temperature change. Therefore, a component having a low linear expansion coefficient (for example, Invar 1.2 [x10 ^-6 / ° C]) is used for the frame 80, and the temperature compensating members 12 and 1 are used.
A rigid body having a positive coefficient of linear expansion as 3 (for example, aluminum 2
3.9 [x10 ^-6 / ° C]). For this reason, there were also problems that the whole mechanism became large, the weight increased, and the material cost was high.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a driving device that can solve various problems in the above-described conventional driving device. And a driving device having the same.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a piezoelectric member formed by stacking a number of piezoelectric ceramic layers that expand and contract by increasing or decreasing a voltage and an internal electrode layer; A single laminated piezoelectric element in which a plurality of parts are alternately laminated, a single frame supporting one end of the laminated piezoelectric element in a direction of expansion and contraction orthogonal to the direction of lamination, and the expansion and contraction of the laminated piezoelectric element. It is characterized by comprising a plurality of actuators provided on the other end side in the direction and transmitting expansion and contraction of the laminated piezoelectric element to an object to be driven.

[Operation] According to the driving device having the piezoelectric element of the present invention having the above configuration, the number of components is reduced by driving a plurality of actuators with a single laminated piezoelectric element and a single frame. As a result, high productivity, small size, light weight, and low cost can be achieved. In addition, since the frame is a common frame, the frame cross-sectional area increases and the frame rigidity increases. Thereby, the loss of the displacement of the element can be reduced.

Furthermore, the laminated piezoelectric element has high tensile strength in a direction perpendicular to the laminating direction and high bending strength in the laminating direction. While the tensile force in the laminating direction and the bending force in the direction perpendicular to the laminating direction act in a direction to separate the piezoelectric ceramic and the electrode, the bending force in the direction perpendicular to the laminating direction and the bending force in the laminating direction. The force does not act in the direction that separates the piezoelectric ceramic and the electrode. In addition, since the common laminated piezoelectric element has the effect of increasing the cross-sectional area of the element, even if a tensile force or a bending force is applied during driving, the laminated piezoelectric element is not likely to be damaged, and the reliability is improved.

Further, unlike the longitudinal effect piezoelectric element, the piezoelectric element using the lateral effect as in the present invention has a positive coefficient of thermal expansion in the direction of expansion and contraction like a general substance. For this reason, less temperature compensating material is required.

Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the laminated piezoelectric element 1 is formed by alternately laminating a plurality of piezoelectric ceramic layers 42 made of lead zirconate titanate ceramic material (PZT) and an internal electrode layer 41 made of silver palladium metal material. 5 and four non-piezoelectric portions 43 made of an organic resin material and having a low elastic modulus are alternately laminated. The piezoelectric portion 40 contracts in a direction perpendicular to the laminating direction (horizontal direction in the figure) by applying a voltage, and expands by removing the voltage. The laminated piezoelectric element 1 is used in this expansion and contraction direction. The so-called horizontal effect of the piezoelectric body portion 40 is used, and the piezoelectric body portion 40 is used in a direction different by 90 ° from the case where the conventional vertical effect is used. In this case, the linear expansion coefficient of the multilayer piezoelectric element 1 (horizontal direction in the drawing) is positive due to the effect of releasing the strain accompanying the polarization at the time of temperature rise, for example, 2.0 to 9.0 [x1
0 ^-6 / ° C].

Here, a method for manufacturing the laminated piezoelectric element 1 will be described with reference to FIG. That is, first, a piezoelectric ceramic layer 42 made of lead zirconate titanate ceramic material (PZT) and an internal electrode layer 41 made of silver palladium metal material
Are alternately laminated to form a plate of the piezoelectric body portion 40 by an integral sintering method. Then, five plates of the piezoelectric body portion 40 and a non-piezoelectric portion having a low elastic modulus made of an organic resin material are formed. Forty-three plates are alternately joined to each other via an organic adhesive (not shown). After that, as shown by a dashed line in the same figure, by cutting into a predetermined shape and size, that is, the same shape and size as the laminated piezoelectric element 1, by performing a polarization process through the internal electrode layer 41, Thus, the laminated piezoelectric element 1 shown in FIG. 1 is obtained.

As shown in FIG. 2, the laminated piezoelectric element 1 is attached to a frame 80 composed of a main frame 2 and a sub-frame 4 arranged in a direction perpendicular to the laminating direction (the direction perpendicular to the paper). . These mainframes 2
And the sub-frame 4 has a linear expansion coefficient of 9.0 to 11.7 [x10
⁻⁶ / ° C.]. The sub-frame 4 is fixed to the base 3 of the main frame 2, and the laminated piezoelectric element 1 is fixed to the base 3 via a temperature compensating material 12 at one end in the expansion and contraction direction. The temperature compensating material 12 is made of aluminum having a linear expansion coefficient of 23.9 [x10 ^-6 / ° C], and is fixed to the laminated piezoelectric element 1 and the base 3. The temperature compensating member 12 is provided to make the maximum displacement position of the laminated piezoelectric element 1 always coincide with the normal position. The amount of change in the residual strain of the laminated piezoelectric element 1 due to a rise in temperature is smaller than the amount of expansion of the frame 80, and the maximum displacement position does not reach the normal position. Thus, the unreachable distance of the laminated piezoelectric element 1 is compensated for by the expansion amount of the temperature compensating material 12, so that the maximum displacement position of the laminated piezoelectric element 1 is kept constant.

On the opposite side of the laminated piezoelectric element 1 from the side on which the temperature compensating material 12 is fixed, a total of five movers 5 are fixed to the respective piezoelectric portions 40 by an adhesive. Each mover 5 is
The mover 5 is connected to the main frame 2 by an Eden spring 67 corresponding one-to-one. Each of the Eden springs 67 is provided with a gap between a first leaf spring 6 having one end fixed to a portion of the main frame 2 facing the mover 5 and a gap between the first leaf spring 6. Has a second leaf spring 7 fixed to the mover 5 and a coupling portion 8 for coupling each other end of the first leaf spring 6 to the second leaf spring 7. The arm 10 is fixed to the connecting portion 8 of each Eden spring 67 so as to extend in a direction parallel to the stacking direction of the multilayer piezoelectric element 1, and the printing wire 11 is fixed to the tip of each arm. A total of five print wires 11 are supported by a wire guide 14 formed integrally with the frame 80.
FIG. 3 shows a perspective view thereof. Therefore, the voltage applied to the piezoelectric body 40 of the laminated piezoelectric element 1 is removed, and the piezoelectric body 40
Is extended, the corresponding second leaf spring 7 is moved upward in FIG. 2 with respect to the first leaf spring 6, and the two leaf springs 6 and 7 are elastically deformed so that the connecting portion 8 is moved as shown in FIG. At this time, the arm 10 is rotated counterclockwise and the arm 10 is rotated in the same direction, and the corresponding printing wire 11 is retracted to the non-printing position. When the piezoelectric portion 40 of the laminated piezoelectric element contracts, the corresponding second leaf spring 7 moves in the opposite direction with respect to the first leaf spring 6,
The leaf springs 6, 7 release the stored spring force due to elastic deformation, and the connecting portion 8 rotates clockwise in the figure to rotate the arm 10 in the same direction, and the corresponding printing wire 11 moves toward the printing position. Be moved forward. In the present embodiment, since the direction in which the arm 10 extends from the Eden spring 67 is reversed from that in the related art, the piezoelectric body portion 40 of the multilayer piezoelectric element 1 is formed.
The relationship between the expansion / contraction of the print wire 11 and the forward / backward movement of the print wire 11 is opposite to that in the related art. Although the amount of expansion and contraction of the piezoelectric body part 40 of the laminated piezoelectric element 1 is small,
Numeral 11 moves between the printing position and the non-printing position. In this embodiment, the movable element 5, the Eden spring 67, the arm 10, and the like constitute an operating device.

The first leaf spring 6 and the second leaf spring 7 of the Eden spring 67 include:
A preload is applied when the laminated piezoelectric element 1 is assembled to the frame 80. When the laminated piezoelectric element 1 is assembled to the frame 80, each Eden spring 67 has the first leaf spring 6 fixed to the main frame 2 and the second leaf spring 7 fixed to the mover 5, and the temperature The laminated piezoelectric element 1 to which the compensating material 12 is adhered is inserted between the mover 5 and the base 3 of the main frame 80, and is positioned at a position where the leaf springs 6, 7 are flexed by a certain amount.

When the preload is applied to the Eden spring 67, a moment is generated in each mover 5 to rotate the mover 5 counterclockwise about the center of the mover 5 in the figure, and the Eden spring 67 tilts. May cause printing failure. Therefore, in this embodiment, the four-bar parallel link 16 is provided to prevent the mover 5 from rotating. The four-node parallel link 16 is formed by stamping and bending a leaf spring material. The piezoelectric portion 40 of the laminated piezoelectric element 1 expands, and is elastically deformed as the movable element 5 moves to move. There is a function of generating a clockwise moment in the armature 5 and canceling the moment in the direction of rotating the armature 5 in the counterclockwise direction to prevent the armature 5 from rotating, thereby preventing printing defects. In addition, since the rotation of the mover 5 is prevented, each piezoelectric portion 40 of the laminated piezoelectric element 1 can expand and contract linearly without bending, and no bending force is applied.

In the printing device configured as described above, when printing is not performed, no voltage is printed on the piezoelectric body portion 40,
The five printing wires 11 are retracted to the non-printing position. At the time of printing, five printing wires 11 are used.
Are applied and removed selectively according to the print data, and printing is performed. At the time of printing, a voltage is applied to the piezoelectric body portion 40, and the corresponding printing wire 11 is moved toward the printing target by contraction. However, at the time of non-printing, the Eden spring 67 is bent by the extension of the piezoelectric body portion 40. And the energizing force is stored. Therefore, the printing wire 11 is moved toward the printing position by the urging force of the Eden spring 67 released by the contraction of the piezoelectric body portion 40 and the tensile force of the piezoelectric body portion 40, and the moving speed and the stroke are increased. In addition, printing can be performed with good responsiveness to a printing command, and the effect of clear printing can be obtained.

When the printing wire 11 is moved to the printing position in this way, the piezoelectric body portion 40 is rapidly contracted by the application of a voltage, whereas the mover 5 and the arm 10 try to stay there by inertia, A tensile force is applied to the body 40. However, since the laminated piezoelectric element 1 drives the printing wire 11 by expansion and contraction in a direction perpendicular to the laminating direction, the laminated piezoelectric element 1 is strong against tensile force and does not break. In addition, the laminated piezoelectric element 1 is configured so that the four-node parallel link 16 expands and contracts without bending by regulating the inclination of the mover 5, but the mover 5 is not necessarily inclined at all. However, the laminated piezoelectric element 1 is strong against bending force in the laminating direction and does not break. Further, in the laminated piezoelectric element 1, five piezoelectric members 40 are joined via the non-piezoelectric member 43, and the element cross-sectional area is larger than that of the piezoelectric member 40 alone. Strength against bending force is further increased, and reliability is improved.

Further, since the piezoelectric portion 40 of the laminated piezoelectric element 1 has the same positive temperature characteristics in the expansion and contraction direction as the thermal expansion of the frame 80, the frame 80 can be made of an inexpensive material having a large linear expansion coefficient. The cost of the apparatus can be reduced, and the amount of compensation of the temperature compensating material 12 can be reduced, so that the apparatus can be downsized and the weight of the apparatus can be reduced.
If the amount of change in the residual strain of the piezoelectric body portion 40 and the amount of thermal expansion of the frame 80 can be made the same, the temperature compensating material 12 can be omitted, further reducing the device cost, weight, and dimensions. be able to.

In addition, the driving device of the above embodiment is composed of one laminated piezoelectric element 1 and one frame 80 despite driving a plurality of actuators, so that the number of parts is reduced and productivity is very good. Cost can be reduced. Further, the size and weight of the entire printing apparatus can be reduced. Further, in the laminated piezoelectric element 1, as shown in FIG. 1, the laminating direction of the piezoelectric body portion 40 and the non-piezoelectric body portion 43 and the laminating direction of the piezoelectric ceramic layer 42 and the internal electrode layer 41 match. After alternately laminating and integrally sintering the piezoelectric ceramic material constituting the piezoelectric ceramic layer 42 and the metal material constituting the internal electrode layer 41, an organic resin material constituting the non-piezoelectric portion 43 Can be manufactured by adhering a plurality of sheets through a substrate, cutting the resultant into a predetermined shape, and performing a polarization treatment. When the conventional vertical effect laminated piezoelectric element 70 shown in FIG. 6 is to be joined via a plurality of non-piezoelectric portions, the laminating direction of the piezoelectric ceramic layer 42 and the internal electrode layer 41 and the vertical effect laminated piezoelectric element 70 Since the lamination direction of the and the non-piezoelectric portion is orthogonal, the production requires many steps. Therefore, the productivity of the multilayer piezoelectric element 1 according to the present invention is higher than that of the conventional element.

The driving device having the piezoelectric element according to the present invention is not limited to the above-described embodiment, and the present invention may be implemented in a form in which various modifications and improvements are made based on the knowledge of the parties without departing from the scope of the claims. Can be implemented. For example, the number of piezoelectric members 40 and the number of non-piezoelectric members 43 of the laminated piezoelectric element 1 may be increased to increase the number of dots of the driving device.

If necessary, each of the Eden springs 67 can be formed as an integral structure. At this time, the leaf spring on the main frame 2 side of the Eden spring 67 is formed integrally, and the leaf spring on the mover side is formed individually for each mover 5.

Also, the four-bar parallel link can be formed integrally.

[Effects of the Invention] As is clear from the above description, according to the driving device having the piezoelectric element of the present invention, a plurality of actuators are driven by a single laminated piezoelectric element and a single frame. A small-sized, light-weight, and low-cost drive device with a small number of parts, high productivity, and a low cost can be obtained. In addition, since the frame is a common frame, the frame cross-sectional area increases and the frame rigidity increases, so that the loss of element displacement can be reduced.

Furthermore, the laminated piezoelectric element has a high tensile strength in a direction perpendicular to the laminating direction and a high bending strength in the laminating direction, and also has a large element cross-sectional area because it is a common laminated piezoelectric element. Even if a force is applied, there is no possibility that the laminated piezoelectric element will be damaged, and the reliability of the driving device is improved.

Further, in the driving device of the present invention, there is generally no need to use a high-weight temperature compensating material, so that there is an effect that the driving device can be configured with a low weight.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a laminated piezoelectric element of a driving device for a wire dot type printing device according to an embodiment of the present invention, FIG. 2 is a front view of the driving device, and FIG. FIG. 4 is a perspective view of a laminated piezoelectric body in which a piezoelectric body part and a non-piezoelectric body part are laminated. FIGS. 5 and 6 illustrate a conventional device.
FIG. 5 is a front view of the driving device, and FIG. 6 is a perspective view of the laminated piezoelectric element. In the figure, 1 is a laminated piezoelectric element, 5 is a mover, 9 is a driving device, 10
Is an arm, 11 is a print wire, 40 is a piezoelectric body portion, 41 is an internal electrode layer, 42 is a piezoelectric ceramic layer, 43 is a non-piezoelectric body portion, 67 is an Eden spring, and 80 is a frame.

Claims (1)

(57) [Claims] 1. A single laminated piezoelectric element comprising a plurality of piezoelectric members each formed by laminating a number of piezoelectric ceramic layers and internal electrode layers which expand and contract according to an increase and decrease in voltage, and a plurality of non-piezoelectric members laminated alternately. A single frame that supports one end of the laminated piezoelectric element in the direction of expansion and contraction perpendicular to the direction of lamination, and is provided on the other end of the laminated piezoelectric element in the direction of expansion and contraction;
A driving device having a piezoelectric element, comprising a plurality of actuators for transmitting expansion and contraction of a laminated piezoelectric element to an object to be driven.